Genetically engineered tomato

Ulrich Ulrich
Wed Feb 15 10:01:37 EST 1995


Whereas antibiotic resistances encoded in plasmid DNAs can be rapidly lost
in the absence of selective pressure, this is due to the loss of the
plasmid
element.  When antibiotic resistance genes are present in the chromosomal
DNA, the rate of loss is much much less.  In the case of transgenic
plants,
the resistance genes are integrated in the chromosomal gene and are thus
a valid source of concern.  Strategies to later remove the selectable
gene,
such as by use of a site specific recombination system have been devised.

Ulrich Melcher
Oklahoma State University

In article <HACHEYB.95Feb13131601 at bmerh9f2.bnr.ca> hacheyb at bmerh9f2.bnr.ca
(Brian Hachey) writes:
>In article <Pine.SOL.3.91.950212214546.18636D-100000 at corona> Patrick
O'Neil <patrick at corona> writes:
>
>> From: Patrick O'Neil <patrick at corona>
>> Newsgroups: bionet.plants
>> Date: Sun, 12 Feb 1995 21:56:42 -0700
>> Organization: University Of Utah Computer Center
>> 
>
>[Stuff related to the original thread deleted]
>
>> If, on the other hand, 
>> you grow that transformed bacteria in non-ampicillin media for a week
or 
>> so - let's say, to be safe, three weeks - at the end of that time, you 
>> will most likely find no bacteria resistent to the antibiotic.  The
gene 
>> will have mutated, and why not?  There is nothing selecting for a 
>> functional copy of the gene.  Moreover, the entire plasmid that
harbored 
>> the gene in the first place is liable to be lost entirely unless it 
>> carries another gene that gives selective advantage in the
circumstances 
>> within which the bacteria finds itself.  My long-winded reply is meant
to 
>> state that the threat is still minimal since the genes for antibiotic 
>> resistence are not "coded in stone" and they mutate into nothingness
when 
>> no antibiotic is present within relatively few turnovers.
>
>I find this quite interesting, but unfortunately I have very little
>knowledge about the subject.  That being the case, I hope you'll forgive
>these possibly ignorant questions.  Do genes really mutate that quickly?
>What is the mutation rate and what is the average redundancy in a
>gene?  I suppose my question really boils down to, given a medium
>which does not favour a specific gene, what is the average number of
>generations needed for that gene to be mutated out?  Also, if the
>number of generations is small, I suppose that most macroscopic
>organisms have lots and lots of redundant genes...  Hmm...  I suppose
>I really should read an intro to genetics.  Any suggestions?
>
>             Thanks for the info,
>                      Mike
>





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